The present invention relates to chokes or starting aids for small internal combustion engines and more particularly, to a choke or starting aid which is responsive to the vibration of the internal combustion engine upon start-up of the engine.
When starting small internal combustion engines, it is usually necessary to pull on the starter rope several times before the engine kicks over and begins to run. Generally, after a couple of pulls on the starter rope the engine starts and runs for a short period of time and then stops. This is what is commonly known in the field as a "false start". This "false start" phenomenon has been present in the chain saw art for several years and has come to be accepted by the users of such saws as an acceptable starting method. The user generally has knowledge of the fuel system procedure and understands why the system is not starting.
The difficulty in starting a cold small internal combustion engine centers around the choke system of these particular engines. When the choke system is in a closed position, the fuel line system of the cold engine has a very high restriction in the air intake. This restriction of the air intake forms a vacuum in the fuel line, sucking fuel into the engine via the carburetor from the fuel tank. As the starting rope is pulled,the engine sucks fuel into the carburetor by the vacuum created in the system. As the engine begins to fire, a certain amount of air is necessary to keep the engine running. With a manual choke, the user must open the choke quickly after the engine begins running or the user will experience the "false start" phenomenon. The reason for the "false start" is that as the speed of the engine increases, the engine sucks more fuel. With the choke in a closed position however, the amount of air flow entering the engine is not increased. Thus a proper mixture of air and fuel is not achieved and the engine dies instantly. Also, if the engine does not start up, a substantial amount of fuel is sucked into the engine, via the carburetor causing the engine and carburetor to become flooded, further hampering the starting procedure of the engine.
Choke devices presently used in the field are of the butterfly type. These types of chokes are pivotally secured in the carburetor air port of an internal combustion engine. The choke usually pivots about a central axis, flipping from a closed to an open position. This type of choke assembly has several disadvantages. The choke is either in a fully closed or a fully open position. When starting the engine the choke is in the fully closed position. Once the engine starts, it is nearly impossible to rotate the choke to its open position, so that the engine will continue to run. Also, the butterfly valve may slip from a closed to an open position without notice to the user. This slippage is due to the fact that, in many instances, there is no resistance member holding the butterfly valve in position. Those skilled in the art are aware of yet other disadvantages of this type of choke assembly.
Accordingly, it is an object of the present invention to overcome the disadvantages of the above art. The present invention provides the art with a new and improved choke assembly which enables air to automatically enter the carburetor during the start-up of an internal combustion engine for providing a continuous running situation. The present invention includes a resilient biasing member for securing the choke assembly in place against slippage. Further, the present invention utilizes the vibration of the small internal combustion engine during start-up for enabling air to enter into the carburetor of the engine at start-up.
The new and improved choke assembly of the present invention provides the art with a semi-automatic choke or starting aid. The choke assembly generally is for small internal combustion engines having a carburetor with an air port in communication with the carburetor and combustion air. Also, a bore, through the carburetor, is in communication with the piston cylinder of the internal combustion engine. The choke of the present invention includes a mechanism for controlling an amount of combustion air entering the carburetor. The mechanism includes an inertia valve member positioned in the inlet air manifold for selectively controlling the amount of combustion air entering into the carburetor. A resilient biasing member, secured in the inlet air manifold, resiliently secures the inertia valve member in the inlet air manifold. The inertia valve member and biasing member are responsive to the vibration of the internal combustion engine for controlling the amount of combustion air entering into the carburetor.
Generally, the inlet air manifold is coupled with a seating member which provides a seating surface for the inertia valve in the manifold. The seating member has an aperture for metering the amount of air which enters into the carburetor. Also, the aperture provides the seating surface for the inertia valve member.
From the subsequent description and the appended claims taken in conjunction with the accompanying drawings, other objects and advantages of the present invention will become apparent to one skilled in the art.